1. Field
An aspect of embodiments of the present invention relates to an organic light emitting display and a method for driving the same.
2. Description of the Related Art
Recently, there have been developed various types of flat panel displays that have reduced weight and volume in comparison to cathode ray tubes. The flat panel displays include liquid crystal displays, field emission displays, plasma display panels, organic light emitting displays, and the like.
Among these flat panel displays, the organic light emitting display displays images using organic light emitting diodes that emit light through recombination of electrons and holes. The organic light emitting display has a fast response speed and is simultaneously driven with low power consumption.
The organic light emitting display includes a data driver configured to supply data voltages to data lines, a scan driver configured to supply scan signals to scan lines, and pixels respectively positioned at areas defined by scan lines and data lines (e.g., at crossings of the scan lines and the data lines). The pixel controls current supplied to an organic light emitting diode, based on a data voltage supplied to a gate electrode of a driving transistor.
The pixel of the organic light emitting display can be driven by an analog driving method or a digital driving method. The analog driving method is a method of adjusting the emission amount of the organic light emitting diode by controlling the drain-source current of the driving transistor, based on the data voltage. The digital driving method is a method of adjusting the emission period of the organic light emitting diode by controlling the turn-on of the driving transistor, based on the data voltage.
Specifically, in the digital driving method, one frame is divided into a plurality of subfields, and the organic light emitting diode emits light by turning on the driving transistor in each subfield or does not emit light by turning off the driving transistor in each subfield. Thus, each pixel may represent two gray scale levels in each subfield. As a result, in the digital driving method, each pixel represents gray scale levels, based on a combination of the emission/non-emission of the organic light emitting diode, in each subfield.
Accordingly, in the digital driving method, the gray scale representation ability of the pixel depends on the number of sub-fields. The gray scale representation ability of the pixel refers to how many gray scale levels the pixel can represent. For example, when each pixel is to represent two gray scale levels in each subfield, the pixel may represent 2n (n is a positive integer) gray scale levels according to the number of subframes. In this case, the one frame may be divided into n subfields. For example, when the pixel represents 64 gray scale levels, the one frame may be divided into six subfields. When the pixel represents 256 gray scale levels, the one frame may be divided into eight subfields. However, there is a problem in that as the one frame period is divided into a larger number of subfields, the frame frequencies of the scan and data drivers increase.